1. Field of the Invention
The present invention relates to both an apparatus for automatically generating a data distribution route when a plurality of users on a network receive multimedia data (streaming data), such as the same video, voice, etc., and a method thereof.
2. Description of the Related Art
As shown in FIG. 1, if in the current Internet or a current Intranet, a plurality of clients 13 receive the same streaming data, in most cases the source 11 of the data makes the same number of copies of the data as the number of the clients 13 and transmits them (uni-casts). In this case, the data transmitted from the source 11 are transferred to the clients 13 via a router 12.
In this case, since the same data flow through the same network many times, the network gets crowded and sometimes the streaming data is delayed or discarded. For this reason, clients sometimes cannot receive streaming data smoothly.
To solve such a problem and to smoothly distribute data to a plurality of clients, conventionally, the multi-casting of a network layer or the multi-casting of an application layer are used.
As the network layer multi-casting, IP (Internet protocol) multi-casting is popular. In IP multi-casting, if a source transmits data to a multi-casting address assigned to a specific host group, a router on the network automatically generates a distribution tree leading from the source to the clients and branches data as requested. In this way, a plurality of pieces of the same data can be prevented from flowing through the same network.
However, to use IP multi-casting, the network layer of a router on a route from a source to a client must be modified and an IP multi-casting function must be incorporated there. If someone multi-castings streaming data by mistake, data are spread all over the network, unlike uni-cast. Therefore, there is a possibility that other data traffic may be suppressed.
Thus, IP multi-casting has not been introduced in most domains for the reason that there are problems, such as that a network layer must be modified, that the management methods of both a multi-casting address and streaming data are not established, etc.
The multi-casting of an application layer is a method for efficiently distributing data by generating a distribution tree among hosts and an application (re-distribution server) for copying and branching data at the branch point of the tree. Since in this way, data are distributed by an application, there is no need to modify the network of a router (to incorporate an IP multi-casting function). Therefore, in this case, streaming data can be more easily managed than in the case of the multi-casting of a network layer.
However, the conventional application layer multi-casting described above has the following problems.
Since a distribution tree is manually generated, the manager must understand both the configuration and situation of the entire network and must make an appropriate setting of the allocation of re-distribution servers and the like. Even if an application for automatically generating a tree is used, a setting is also required by the manager since it is assumed that the physical configuration of a network, such as the location relationship of routers and the like, is already known.
Usually, it is impossible or difficult for the manager of the basic part of an Intranet to make the network setting of the terminal of the Intranet. If the network manager and the application manager are different (belong to different departments), it is very difficult to make a multi-casting setting.